A surge driven by the delta variant is receding in the United States, but officials and experts say that increased transmission during the coming colder months remains a threat and that steady rates of vaccination are key to keeping the coronavirus at bay.

The Centers for Disease Control and Prevention said Thursday that about 56% of the U.S. population was fully vaccinated. Providers are administering an average of about 949,000 doses per day, including first, second and additional doses, far below the April peak but higher than the recent Sept. 28 low point of about 625,000, according to a New York Times database.

Surveys from the Kaiser Family Foundation show that vaccine support has been rising out of fear of the delta variant: Almost 40% of newly inoculated respondents said they had sought the vaccines because of the rise in cases, and more than a third said they had become alarmed by overcrowding in local hospitals and rising death rates.

The number of people eligible for vaccinations could also soon increase substantially: Pfizer and BioNTech asked federal regulators Thursday to authorize emergency use of their coronavirus vaccine for children ages 5 to 11, a move that could help protect more than 28 million people in the United States.

The companies say they are submitting data supporting the change to the Food and Drug Administration. The agency has promised to move quickly on the request and has tentatively scheduled a meeting Oct. 26 to consider it. An FDA ruling is expected as early as the end of this month.

Rupali Limaye, a behavior scientist at Johns Hopkins Bloomberg School of Public Health who studies vaccine hesitancy, said that parents’ getting their children aged 5 to 11 vaccinated would be a “huge game changer” because they represent a large proportion of population.

Vaccine mandates have also been taking effect recently, with federal workers and contractors, teachers, health care providers and others compelled to get immunized or risk losing their jobs. Such a requirement for New York teachers spurred thousands of last-minute vaccinations. Tyson Foods reported a 91% vaccination rate ahead of a November deadline, compared with less than half before its mandate was announced in August.

President Joe Biden appealed Thursday for more companies to mandate COVID vaccinations for employees, asking them to take initiative because an effort that he announced last month to require 80 million American workers to get the shot undergoes a rule-making process and may not go into effect for weeks.

A report released by the White House on Thursday sought to show how vaccine mandates had helped persuade more people to receive their shots: Seventy-eight percent of eligible adults have had at least a first dose.

As the country nears colder temperatures that will push many indoors, Dr. Yvonne Maldonado, an infectious disease expert at Stanford, said that the next few months would be critical, but that the combination of increased vaccinations and natural immunity from infections could prevent another catastrophic wave like the one that struck last year.

“Most of us don’t think we’re going to see the terrible surge we saw last winter,” she said. “That was horrific. I hope we never have to live through something like that again.”

This article originally appeared in The New York Times.